Catalytic ignition of the [BMIM]DCA-H2O2 propellant with the Cu(vim)2(DCA)2 complex.

An ionic liquid (IL)-H2O2 propellant offers a green alternative to the traditional hydrazine-N2O4 system. Due to the weak oxidizing ability of H2O2, typical ILs cannot be spontaneously ignited. To address this issue, catalytic ignition was proposed, and a series of metal complex catalysts with the formula M(vim)2(DCA)2 (M = Mn, Fe, Co, and Cu) were synthesized. Single-crystal X-ray diffraction analysis shows that the Mn, Fe and Co complexes adopt an octahedral geometry, while the Cu complex exhibits a planar quadrilateral geometry. The physicochemical properties (T d, ΔH c, ΔH f, and I sp) of the fuels (10 wt% M(vim)2(DCA)2 + 90 wt% [BMIM]DCA) were evaluated. Dynamic light scattering and UV-vis spectroscopy analyses confirm that the four complexes disperse well in [BMIM]DCA. Ignition tests reveal that Cu(vim)2(DCA)2 exhibits the best catalytic performance for the ignition of [BMIM]DCA with H2O2, achieving t id as short as 21 ms. EPR studies indicate that Cu(vim)2(DCA)2 catalyzes H2O2 to generate reactive oxygen species (·OH, ·O2 -, and 1O2), which subsequently induce the spontaneous ignition of [BMIM]DCA. DFT calculations reveal that the zero-dimensional geometry of Cu(vim)2(DCA)2 features an unsaturated Cu center and electron-rich ligand framework. This typical structure enables efficient electron transfer to activate H2O2, boosting ROS generation and ignition. This work clarifies the crucial role of the metal center in the IL-H2O2 system and provides an important insight into the catalytic ignition of the "double-green" propellants.